References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Sexually acquired reactive arthritis (SARA) is joint inflammation that develops as a reaction to an STI — most commonly chlamydia. The infection itself doesn’t infect the joints; instead, the immune system overreacts, causing inflammation in joints, eyes and sometimes the urinary tract. It typically appears 1-4 weeks after the triggering infection.
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What Causes It
| STI Trigger | How Common |
|---|---|
| Chlamydia | Most common trigger |
| Gonorrhoea | Less common |
| Mycoplasma genitalium | Possible trigger |
| Ureaplasma | Possible but uncertain |
Symptoms
- Joint pain and swelling (often knees, ankles, toes)
- Eye inflammation (conjunctivitis)
- Urethritis (painful urination)
- Skin rashes (sometimes)
- Heel pain
- Lower back stiffness
The classic triad is arthritis + urethritis + conjunctivitis, though not everyone has all three.
Who Gets It
- More common in men than women
- Usually in young adults
- Linked to HLA-B27 gene (a genetic predisposition)
- Not everyone with the triggering STI develops reactive arthritis
Diagnosis
- Based on symptoms plus history of recent STI
- STI testing (may be positive or already treated)
- Blood tests for inflammation (CRP, ESR)
- HLA-B27 testing
- Joint imaging if needed
Treatment
- Treat the underlying STI (antibiotics)
- Anti-inflammatory drugs (NSAIDs) for joint pain
- Physiotherapy
- Steroid injections for severe joint inflammation
- Eye drops for conjunctivitis
- Most cases resolve within months
Outlook
- Most people recover fully within 3-12 months
- Some have recurring episodes
- A small minority develop chronic arthritis
- Early STI treatment may reduce the risk
Prevention
- Prompt STI testing and treatment
- Condom use reduces STI exposure
- Regular STI screening
Read more: What is chlamydia? | Untreated STIs | STIs and the eyes
Frequently Asked Questions
Is reactive arthritis an STI?
No — it’s an immune reaction triggered by an STI.
Will it go away?
Usually yes, within months. A small minority have longer-term issues.
Can it be prevented?
Prompt STI treatment may reduce the risk.
Related reading
- What Is a Female (Internal) Condom?
- What Is a Shigella Infection?
- What Is Bacterial Vaginosis (BV)?
- What Is Gonococcal Arthritis?
- What Is Human Papillomavirus (HPV)?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
